Garage Heat Vent

This option might work best for most applications simple setup (shown in video) and you an simply mount over floor or wall vent and comes on with airflow.

http://www.suncourt.com/Equalizer.html

Can be easily removed when not in use.
Also another option is cut a vent sized in wall and you can pull heat/AC into an area.

Actually use this at home and did not think about it until just now.

Heat to the garage is only half the battle in the cyclone, crawled up under it after temps dropping down in to the 20's to see why the floor was so cold and there is no insulation under there. (That I could see anyhow)

Open with exposed steel engineered joists and open to the elements up to the garage decking?!?!? The bath has corplast sealing it but after that nothing last 8-10'.

Looks like another trip to big box center...LOL